A federal research cruise off the Olympic Peninsula coast has revealed new deep-sea boulder fields peppered with bright sponges, small corals and rockfish.

The National Oceanic and Atmospheric Administration (NOAA) cruise, which returned last week from the Olympic Coast National Marine Sanctuary, was the first in a series of summer cruises looking for new deep-water rocky habitats and deep-sea coral fields.

Using high-tech underwater vehicles that take video and still photos, researchers examined critters in the sanctuary’s depths, including petite deep-water corals, bright green sponges and a variety of fish.

“See that little fish tucked into the sponge?” said Elizabeth Clarke, of the Northwest Fisheries Science Center, who was among the lead scientists on the cruise. “Using this technology, you really catch them unawares in their environment and get such a great view of the spatial relationship between the habitat, the invertebrates and the fish.”

The cruise searched for lush deep-sea coral colonies, suspected of being important fish habitat. Researchers chose boulder fields more than 300 feet deep, where corals normally thrive. Their underwater cameras revealed a world absent of large corals, but still thick with other species.

“Although we didn’t encounter the dense coral fields that I would have liked to see,” said Edward Bowlby, research coordinator at the sanctuary and chief scientist on the cruise, “it was quite beautiful to see these underwater boulder fields and all the associated invertebrates, crinoids [sea lilies], sponges and fishes.”

Moreover, bouts of bad weather and high seas made it too dangerous to deploy equipment four out of the six days they were sampling.

Despite the absence of coral, the researchers found an abundance of yellow rockfish, a vulnerable and overfished species.

“We have pretty limited information on yelloweye rockfish because they live in these rugged habitats that are really hard to get to,” Clarke said. “So this new footage should give us a better understanding of where these fish are and how they utilize these rocky habitats.”

As of now, the researchers still aren’t sure why corals would occupy one rocky habitat and not another one nearby. But Pacific Coast cruises through the summer from Washington down to Southern California should provide some answers.

“Deep-sea corals are really incredible habitats,” said Kacky Andrews, program manager for NOAA’s coral-reef conservation program. “We have species that can live up to 4,000 years of age, making them some of the most long-lived species on the planet.”

The corals face tremendous threats, such as damage from fishing gear and ocean acidification, Andrews said. These research cruises will look for damage from fishing gear, while taking water samples to address changes in pH.

They will also take coral samples to determine what species they are and to better understand how fast they grow, all of which will help managers design conservation measures.

“This is a very underappreciated habitat, which we know surprisingly little about,” Andrews said. “We are just beginning to scratch the surface in figuring out where they are and what ecological function they meet.”